Poisoned Poisson

Fish Rendered Scentless by Pollution

Fish living in lakes tainted with metals are losing their sense of smell, prompting worries about dwindling populations, because when dissolved metals contact fish nostrils, their neurons shut down to protect the brain. Fish use their sense of smell to navigate murky waters, find mates and food, and avoid predators.

The effect of metals has been linked to impaired reproduction and growth, but this secondary, “covert toxic” effect is described by Keith Tierney, a University of Alberta assistant professor, this way: “If you can’t smell food or avoid predators, you’re more likely to die.”

The good news from Canadian researchers, as reported in the journal Ecotoxicology and Environment Safety, is that such harm to fish can be reversed. When study co-author Greg Pyle, a professor at Alberta’s University of Lethbridge, and his research team relocated yellow perch from Ontario lakes contaminated with mercury, nickel, copper, iron and manganese to a cleaner lake, the fish regained their sense of smell within 24 hours.

Most of the contaminated lakes involved have a metallic mix, making it hard to determine precisely which pollutants are to blame. Copper is high on the list of suspects; its agricultural and manufacturing use has more than doubled in the United States over the past three decades, according to the Copper Development Association.